LPS 33 epilator and probeholder

ABSTRACT

Method and apparatus for controlling an epilation procedure in which a removal process is adaptively controlled for optimum removal prevention of scarring and minimizing sensation, and profiling RF power supplied as an inverse square of measured impedance based on a normalizing impedance.

This is a Division of application Ser. No. 08/531,189 filed Sep. 19,1995 now U.S. Pat. No. 5,785,708.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is an improvement over the invention disclosed andclaimed in U.S. Pat. No. 4,550,728 to Runyon and Hower, and also relatesto a high frequency probe type epilator.

This invention is concerned with an epilation procedure, and a controlapparatus and a probeholder used in connection with the epilationprocedure.

More particularly, the invention is concerned with precise control ofintensity (power level) and timing and dynamic power control based onimpedance variation. Variations in the depth of insertion and haircharacteristics impact the initial impedance, and the application ofpower to the follicle results in dynamic impedance changes. Theimpedance is measured during the pulse and the power is compensated tominimize skin reaction and sensation to the patient.

The invention is also concerned with a novel probeholder.

2. Description of the Prior Act

The prior U.S. Pat. No. 4,550,728, while it also relates to an RFepilator procedure and is also concerned with safety controls, relied onopen loop electrical circuit characteristics to select power setting.This resulted in non-linear power variations, as well as, uncontrolledresponse to variations in impedance during the pulse. The process of RFepilation is performed by inserting an insulated bulbous tipped probeinto a follicle and applying a controlled burst of RF energy to theprobe. The probe tip concentrates the energy at the germinative portionof the hair (dermal papilla) destroying the follicle's capacity toregenerate itself. Operators, based on their experience, select thetiming and intensity of the RF power pulse to be applied. The actualpulse length will not exceed these settings. During the pulse the powerdelivered is based on the intensity setting selected by the operator asimpacted by the inherent response of the circuit to variations of theimpedance reflected to the power amplifier output. The impedance as seenat the probe tip varies throughout the duration as a function of skincharacteristics, hair size and depth of penetration. During the pulsedynamic changes in the impedance occur as energy is applied to thetissue.

With the prior heretofore known probeholders, an operator using theprobeholder became part of the RF load. Different operators presented adifferent load impedance to the circuit based on their own individualtreatment technique. Specifically, as presently understood, the priorheretofore probeholder terminated the coaxial cable center conductorinto a large brass tip which accepted the probe. The shield terminatedwhere the center conductor connected to the end of the probeholderallowing RF energy to be coupled to the operator, as well as thepatient.

SUMMARY OF THE INVENTION

A primary purpose of any improvement in connection with the electrolysisprocedure is to reduce discomfort, prevent scarring and eliminateregrowth. Specifically, as noted heretofore, it is desired to destroythe germinative portion of the hair by treating each follicle just once.This is achieved by concentrating the energy at the tip of the probe atthe dermal papilla. Based on operator training and experience and theuse of the novel circuitry and novel probeholder of this invention, andthe flexible insulated bulbous tipped probe, complete destruction of thegerminative portion of the hair takes place, regrowth is eliminated andthe follicle itself together with its appendages (sebaceous gland andarrector muscle) are left intact and functioning normally.

The operator, based on experience and observation of the removalcharacteristics, will select appropriate time and intensity settings toensure patient comfort and easy removal. Timing can be selected in therange of 1 to 100 milliseconds, and intensity can be selected in therange of 2.5 to 25 watts. The operator then inserts the probe into thefollicle, steps on a foot pedal to activate the machine, withdraws theprobe and lifts the hair out of the follicle with a forceps.

With the invention described herein, it is possible to record theimpedance presented to the power amplifier and power delivered to thematching network during the pulse. The unit is adjusted to a dummy load,equivalent to a nominal hair follicle, to present a nominal impedance of50 ohms to the amplifier. During a removal, it was observed that theinitial impedance is in the range of 50 to 60 ohms. As the power isapplied and tissue heating occurs the impedance reduces by approximately10 percent. The reduction of impedance occurs as a result of softeningof the tissue which allows better probe tip contact. If energy isapplied too rapidly, the destruction of the tissue at the probe tipresults in a rapid increase in impedance. This characteristic, termed as"decoupling", occurs because of the appearance of vapor at the tip. Whendecoupling occurs energy is no longer efficiently transferred to thebase of the hair. If the amplifier is capable of delivering constantpower to the probe, the sudden increase in impedance will result inhigher voltage being applied to the surrounding tissue. Observation ofthe decoupling phenomenon led to the erroneous conclusion that theprocess of removal was complete when decoupling occurred. This wasproven by configuring the unit to terminate the pulse when decouplingwas sensed. In this mode of operation removals were inconsistent, andpain and skin damage still occurred.

These observations have led to the conclusion that it is not onlynecessary to destroy the tissue at the base of the hair, but it is alsonecessary to soften the sheathing around the hair to allow it to slideout of the follicle. Excessive power after decoupling can result in skindamage, and drying of the hair and/or sheathing which makes removaldifficult.

An object of the invention is to accommodate variations in the removalprocess resulting from variations in hair characteristics and depth ofinsertion. The operator's experience is still essential to making aproper insertion and in determining proper settings of time and initialpower based on quality of removal and patient comfort. To meet thisobjective, the power during the pulse is adjusted automatically based onthe impedance presented at the power amplifier output. The powerresponse to impedance variation, because of the use of themicrocomputer, can be programmed to be any response. It has beendetermined that profiling the power as an inverse square of the measuredimpedance works well. To perform this task, the microcomputer sets theinitial power assuming a nominal 50 ohm impedance. Once the pulse isstarted, the impedance is measured every millisecond and the power isadjusted accordingly.

FURTHER OBJECTS OF THE INVENTION

Another object of the invention is to ensure consistency betweenmachines. This is accomplished by use of the microcomputer working inconjunction with the RF amplifier circuity. During the alignment andcalibration process the performance monitor circuitry is calibrated andconstants are saved in the internal battery backed-up RAM. Alinearization table is then generated which relates DAC output to poweroutput into a 50 ohm resistive load as measured by the performancemonitor. Thus the operator is assured that intensity corresponds fromone machine to another.

A further object of the invention is to protect the patient from theinadvertent or misapplication of RF power. This is embodied in the useof the slave microcomputer which independently monitors pulse timing andmust cooperate with the main microcomputer to enable the RF amplifierchain. In the idle state between pulses, power supply voltages areremoved from the Driver and Final Amplifier stages. The RF oscillatorand low level driver are also disabled. Then the linear modulator is setfor minimum output.

To activate the chain the RF oscillator is enabled and the slavemicrocomputer is issued the pulse parameters to be used. The twomicrocomputers then enable the power supply voltages to the Driver andFinal Amplifiers. Two separate outputs from each microcomputer mustagree to enable the Driver power supply, and similar outputs arerequired to enable the Final power supply. Failure of any one of thefour outputs from either the master or slave microcomputers willprohibit the generation of a RF pulse. RF power is then enabled by themain microcomputer by enabling the linear modulator and low leveldriver. This also causes the slave microcomputer to begin independentlytiming the pulse. Under normal conditions the master computer willterminate the pulse, however, if it should fail, the slave processorwill take over and inhibit the output.

A still further object of the invention, as embodied in the improveddesign of the probeholder, is to eliminate the variation of performancedependent on how the operator held the probeholder. As set forthheretofore, this prior design terminated the coaxial cable centerconductor into a large brass tip which accepted the probe. The shieldterminated where the center conductor connected to the end of theprobeholder allowing RF energy to be coupled to the operator, as well asthe patient. The operator, therefore, became part of the load. Asembodied, the improved probeholder design isolates the operator, so thathow the probeholder is held, the angle of the operator's hand, andwhether the operator is touching the patient is no longer a significantfactor.

Other objects, advantages and the nature of the invention will becomeapparent from a consideration of the detailed description taken inconnection with the following figures of the drawings.

FIG. 1 is a block diagram of a microcomputer based epilator circuitryand apparatus according to the invention;

FIG. 2 is a front panel board and includes a microcomputer for drivingthe graphics display and push button switches for operator input;

FIG. 3 is an RF board including power supply components, RF amplifierchain, performance monitor, and matching network forkdriving theprobeholder;

FIG. 4 is a main computer board for controlling and monitoring the RFboard, and interfacing to the operator via the front panel board;

FIG. 5 is a pictorial view of a probeholder according to the invention;and

FIG. 6 is a sectional view of an improved probeholder coaxialtermination according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now more particularly to the drawings which illustrate thebest mode presently contemplated for carrying out the invention, themicrocomputer based epilator apparatus includes a front panel PC board(FPB) 10, an RF power amplifier board (RFB)12 for driving the novelprobeholder 14, and a main computer board (MCB) 16. The unit is poweredfrom either 120 or 230 VAC, 50/60 Hz as derived from the power supplyinterface 18.

Front panel board 10, as shown in detail in FIG. 2, is devoted tooperator interface and includes front panel switches 20, an 80C31microcomputer 22, graphics display driver 40, and a 480 by 64 pixelgraphics LCD display 24. The main computer board 16 interfaces to theswitches via inputs 28 and outputs 30.

The graphics display interface consists of microcomputer 22, an 80C31,graphics display driver IC 40, and video RAM 38. The graphics displaydriver IC 40 directly interfaces to the graphics display 24. Programmemory for microcomputer 22 is contained in EPROM 42 which also containscustom character generation tables for the graphics display. Displaycommands are sent by the main microcomputer 16 over an opticallyisolated serial link comprising line 34 and optical isolator 36 to themicrocomputer 22. A display confidence indication is provided via line32.

The operator selects the intensity and timing for the pulse to beapplied to the patient by activation of the push button front panelswitches 20. Readback of selected timing and intensity is provided bygraphics display 24. Additional features supported by the front panelprovide for treatment and area timing, as well as, a time of day clock.

The RF board 12 as shown in FIG. 3 contains the circuitry to generate alinearly variable RF pulse with a maximum power output of 25 watts intoan impedance of 50 ohms. The major components of the RF subsystem RFB 12are a 27.120 MHz crystal oscillator 50, linear modulator 52, a low leveldriver 72, 2 watt driver stage 53, FET final RF amplifier 54, harmonicfilter 56, RF V and I sampler 58, and an LC matching network 60. Theboard also contains the power supply rectifiers, filters and regulators64 to develop a 12 VDC for the low level RF circuitry, and power supplyrectifiers, filters and regulators 66 to develop 28 VDC to power finalRF amplifier 54. A separate 5 VDC regulator 74 provides power for theoscillator 50. RF enable 76 controls application of power to the lowlevel RF circuits. The driver amplifier enable 78 requires two inputs148 and 150 from the main computer board 16 (FIG. 4) to be in the activestate before power is applied to the driver stages. Similarly, finalamplifier enable 68 requires inputs 130 and 132 to be satisfied beforepower can be applied to the final amplifier 54. Independent logicsignals 102 and 112 from the main computer board 16 (FIG. 4) enable theoscillator 50 and low level driver 72.

The RF final amplifier 54 is a N-channel FET operating as broadbandClass B linear amplifier. An output loading of 11 ohms is realized by a4 to 1 broadband transformer that drives harmonic filter 56. Theharmonic filter 56 is a seven pole low pass filter tapered to present 44ohms at its input when loaded with a nominal 50 ohm output. The nominalpower output is 25 watts at the output of the harmonic filter. Class Bbias is provided by an adjustable regulator.

Outputs 66a and 66b from the 28 VDC power supply 66 are 0 to 5 voltanalog signals proportional to final voltage and current which input tothe ADC located on the main computer board 16 (FIG. 4). Output 78a fromthe driver enable circuitry 78 provides an analog readback to the ADClocated on the main computer board 16 (FIG. 4) proportional to driver DCvoltage.

RF V and I sampler 58 provides RF voltages proportional to load voltage58a and load current 58b. These outputs separately drive lineardetectors 80 and 84 to derive outputs 80a and 84a which are 0 to 5 voltsignals proportional to the load voltage and current, respectively.Signals 58a and 58b are also used to drive a phase detector 82 whichproduces an output 82a from 0 to 5 volts, centered about 2.5 volts,proportional to the sine of the phase angle between the two inputs. Themain computer samples these voltages to compute power output and themagnitude and phase of the load impedance.

The LC matching network 60 is necessary to transform the impedancereflected from the probe tip through the probeholder cable and theinternal 50 ohm cable 62 to a nominal 50 ohms at its input. Because thetotal cable length of the probeholder and internal cabling approximatesa quarter wavelength, the high impedance at the probe tip is transformedto a low impedance at the output of the matching network.

Referring now to FIG. 4, the main computer board 16 provides theintelligence to monitor the RF subsystem 12 and interface to theoperator via the front panel 10. The main computer 100 is an 80C32microcomputer operating with external program memory as provided byEPROM 114 which resides on the microcomputer bus 90. The microcomputerbus 90 also interfaces to data memory RAM 118 via a battery back-upsocket 116, a 12 bit parallel DAC 108, and keyboard and I/O circuits 152and 158.

Battery back-up to the RAM 118 is essential to maintaining calibrationconstants and linearization table needed for normal system operationduring periods when power is not available. In addition, the batteryback-up socket 116 provides a time of day function.

The microcomputer 100 scans the front panel switches as a 4 by 4 keypadusing four of the eight outputs available from Keyboard and I/O Out buslatch 158. Readback of the keys is provided by four of the eight inputsKeyboard and I/O In circuit 152. One of the remaining outputs from 158are used to enable the sonalert 160 which provides audible feedback tothe operator that an RF pulse has been generated. Another of the outputsfrom 158 provides a high speed, start-stop, serial data stream to thefront panel display microcomputer board 10 via line 34. A confidenceread back from front panel display microcomputer board 10 is provided byline 32 driving the optical isolator 154. This signal is polled by themicrocomputer 100 via one of the inputs of 152.

The foot switch FP, via connector 190 over line 190a, interfaces tooptical insolator 156, and is used by the operator to initiate a pulse.This signal is sensed by the microcomputer 100 using one of the inputsof 152.

The microcomputer 100 sets the required power level via the 12 bit DAC(digital-to-analog converter) 108 over the microcomputer bus 90. The DACoutput is buffered by amplifier 104 to drive the linear modulator 52 vialine 104a.

A high speed serial bus 134, under the control of microcomputer 100,interfaces to the slave microcomputer 110 and the 8 channel, 12 bit ADC106. The purpose of the 87C751 slave microcomputer 110 is to monitor thetiming of the RF pulse and cooperate with the main microcomputer 100 inthe generation of the RF pulse. To perform the function, it is necessaryfor the main microcomputer 100 to communicate the pulse length and pulsecommands to the slave microcomputer 110.

Four direct port I/O pins from each microcomputer, 100 and 110, mustagree to enable an RF pulse. The four signals from each microcomputerdrive separate AND gates 126, 128,144 and 146. Failure of any one of theeight signals will prohibit generation of a RF pulse, or terminate apulse in process. The outputs of AND gate 126 and 128 are used tocontrol power supply voltage to the final amplifier via final amplifierenable 68 over lines 130 and 132. Likewise, AND gates 144 and 146 enablethe driver power supply voltage over lines 148 and 150. Microcomputeroutput 112 is used to enable the low level driver 72, and to trigger theslave microcomputer 110 which starts the independent timer function ofthe slave microcomputer,

The serial 8 channel, 12 bit ADC 106 (analog-to-digital converter) isread by microcomputer 100 to monitor RF pulse parameters such as RFvoltage 80a, RF current 84a and the phase difference between RF voltageand current 82a. In addition, final voltage 66a, final current 66b, anddriver voltage 78a are measured. As a confidence check, the DAC output104b can be read via the ADC 106 to confirm the presence of the RFboard. The power output and load impedance can be calculated from thethree RF parameters measured.

During a pulse, the three RF parameters, voltage, current, and phase,and final voltage and final current are measured every millisecond andsaved in RAM. The main computer, after taking the readings, computes themagnitude of the load impedance and outputs a new DAC valuecorresponding to the power appropriate for that impedance. The RS-232interface 120, along with connector 192 and signal lines 192a, is usedin conjunction with an external IBM-PC compatible computer to controland monitor the epilator performance. In the calibration process,calibration constants are derived for the RF detectors 80, 82 and 84, aswell as, the final voltage and current samplers. These constants arethen downloaded to the epilator and retained in RAM 118. The last stepin unit calibration is generation of a level calibration table. Thepurpose of the level calibration table is to allow interpolation ofdesired intensity setting, selected by the operator as a number from 10to 99, to a corresponding DAC value. Because the calibration constantsand level table are essential to normal operation checksums aremaintained which allow validation of the table values.

The board contains the rectifiers, filter capacitors and regulators todevelop +5 VDC 182, and +12 VDC 186 and -12 VDC 184. The +5 VDC is usedfor the logic circuits while the +12 VDC and -12 VDC are used to powerthe low level analog circuits. Isolation between the analog and digitalsupplies is provided by separate secondary windings outputs 180a and180b of transformer 180.

The case mounted parts as shown in FIG. 3 include two power transformers170 and 180, a line interface module 172, a foot switch connector 190,and an RS-232 interface connector 192. A power source PS is selectableto be 120/230 VAC, 50/60 Hz. Separate power transformers 170 and 180 areessential to maintaining isolation between the high power RF circuitryand the low level analog and digital circuitry.

The probeholder assembly represents one of the major changes in theepilator. Prior art probeholder designs made the operator a part of theRF path because of a large brass piece designed to hold the probe. Sincethis piece was connected to the cable center conductor, significantcapacity coupling to the operator resulted in a circuit such that theoperator was in parallel with the load presented by the patient. Theactual loading of the probe was, thus, variable depending on how theoperator held the probeholder, whether the operator was touching thepatient, as well as, the angle of the operator's hand relative to thepatient.

To isolate the operator, the probeholder was redesigned to extend thecoaxial structure to the end of the probeholder. In the process,intentional capacity of approximately 30 pF was added to the end of thecoaxial cable. The purpose of the added capacity is to limit the RFvoltage at the end of the cable when the probe is not loaded.

Referring to FIG. 5 which shows a novel epilator probeholder 14comprising a BNC connector and housing 204, a coaxial cable 202, handle200, protective tip 210, and replaceable probe 232. An adjustable coil206, located in BNC housing 204, provides for a means for standardizingthe probeholders to present a substantially equivalent impedance at theBNC connector when terminated in to a standard load.

Referring to FIG. 6 which shows the internal construction of the cabletermination and probe interface. The inner conductor 220 of the coaxialcable is soldered 242 to one end of the cylindrical Beryllium Copperfemale connector 224. The other end of 224 is designed to accept andhold the probe 232 in opening 244. A layer of Kapton® is used toinsulate the inner conductor 220 and brass piece 224. A controlledcoaxial capacitor in then formed by adding a layer of copper tape 215over the Kapton® tape and outer conductor 218 of the coaxial cable. Thecopper tape is soldered to the outer conductor. The completed assemblyis positioned in the threaded sleeve 214 and solder 240 is applied tothe outer conductor and sleeve.

The nylon handle 200 threads onto 214 and protects the cable 202.Protective tip 210 threads on the other end of 214, and is removable toallow the operator to change the probe 232.

The actual circuit implementation establishes a preferred embodiment ofthe invention. The improvements are: 1) the ability to profile the poweroutput based on the measured impedance during the removal pulse; 2)improved protection of the patient by use of the slave microcomputer;and 3) the structure of the probeholder to add capacity and eliminatestray capacity effects produced by the operator holding the probeholder.The features realized by using the microcomputer according to theinvention include complete control and monitoring of the RF pulse whichallows, in conjunction with an external computer, analysis of theremoval characteristics of each pulse.

What is claimed is:
 1. An epilation procedure comprising the stepsof:monitoring a removal process; adaptively controlling said removalprocess for optimum removal, prevention of scarring and minimizingsensation; and profiling RF power supplied as an inverse square ofmeasured impedance based on a normalizing impedance.
 2. The epilationprocedure of claim 1, comprising:applying a controlled burst of the RFpower to an epilator probe, said probe concentrating RF energy at thedermal papilla of the hair; and selecting a time period between 1 and100 milliseconds and an intensity in a range of 2.5 to 25 watts forapplication of the RF power to the epilator probe.
 3. The epilationprocedure of claim 1, comprising:measuring impedance presented to anepilator probe, adjusting the RF power supplied to the epilator probe inaccordance with a response to the impedance presented to the epilatorprobe, and independently monitoring pulse timing to enable the RF chain.4. A process for epilation comprising:during a pulse, measuring RFimpedance parameters including measuring RF voltage, RF current and RFphase; monitoring an epilation process and adaptively controlling theepilation process for optimum removal to prevent scarring and minimizesensation; adjusting RF power output based on said RF impedance duringan output pulse; and profiling the RF power supplied to a probe as aninverse square of the measured impedance.
 5. The epilation process ofclaim 4, including adjusting the RF power based on an impedancepresented to a power amplifier which is responsive to microcomputercontrol.
 6. The epilation process of claim 4, wherein during said outputpulse measuring the three RF parameters and final voltage and finalcurrent, and periodically storing measured values, and after the outputpulse is complete, accessing the measured values by an externalcomputer.
 7. The epilation process of claim 4, wherein the three RFparameters measured are voltage, current and phase.
 8. The epilationprocess of claim 4, comprising:selecting a time setting in the range of1 to 100 milliseconds; selecting an initial intensity range between 2.5to 25 watts; activating an epilator apparatus for producing a pulseafter inserting a probe into a follicle; and removing of the hair fromthe follicle with forceps after removing the probe.
 9. The epilationprocess of claim 8, including means to accommodate for a variation inthe removal process responsive to variations in hair characteristics anddepth of probe insertion.
 10. An epilation system, comprising:means formeasuring RF impedance and RF power presented to an epilation probe;means including a microcomputer responsive to the impedance presented bythe epilation probe for adjusting the RF power supplied to the probe;and means for automatically measuring probe RF impedance and RF powerperiodically after commencement of a pulse.
 11. The epilation system ofclaim 10, wherein the measuring means measures the RF impedance and RFpower every millisecond for adjusting the RF power.
 12. The epilationsystem of claim 10, including a slave microcomputer to independentlymonitor pulse timing and cooperating with the means including the mainmicrocomputer to prevent an inadvertent application of RF power.
 13. Theepilation system of claim 12, wherein said measuring means includesmeans for measuring the impedance every millisecond for adjusting power.14. Apparatus for controlling an epilation procedure comprising:meansfor monitoring a removal process; means for adaptively controlling saidremoval process for optimum removal, prevention of scarring andminimizing sensation; and means for profiling RF power supplied as aninverse square of measured impedance based on a normalizing impedance.15. The apparatus of claim 14, including;a main microcomputer, means formeasuring RF impedance and RF power presented by an epilator probe,means adjusting the RF power supplied to the probe in accordance withthe said main microcomputer's response to the impedance presented by theepilator probe, and means independently monitoring pulse timing andcooperating with the main microcomputer to enable the RF chain.
 16. Theapparatus of claim 15, comprising:means for applying a controlled burstof RF power to an epilator probe, said probe concentrating the RF energyat a dermal papilla of a hair; and means for selecting a time periodbetween 1 and 100 milliseconds and an intensity in the range of 2.5 to25 watts for application of the RF power by the epilator probe to thedermal papilla.
 17. The apparatus of claim 14, comprising:means forapplying a controlled burst of RF power to an epilator probe, said probeconcentrating the RF energy at a dermal papilla of a hair; and means forselecting a time period between 1 and 100 milliseconds and an intensityin the range of 2.5 to 25 watts for application of the RF power by theepilator probe to the dermal papilla.
 18. The apparatus of claim 17,including:means for matching a nominal hair impedance to present animpedance of nominally 50 ohms to an RF power amplifier comprising aprobeholder for said epilator probe and an impedance transformationnetwork.